Gene Expression

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Transcript Gene Expression

Gene Expression:
Protein Synthesis
(From a gene to a protein)
Stated Clearly - What is a Gene?
Review of DNA
• DNA is the genetic material
• DNA codes for different genes
– Genes are sections of DNA that code for a specific protein
which determines different traits
DNA is made up of nucleotides
Which contain:
- a phosphate group
- a sugar (deoxyribose)
- a nitrogenous base
Structure of DNA
Central Dogma “Big Idea”
The first step in decoding a genetic message from DNA is
to copy it into RNA. Called Transcription.
Central Dogma
The second step in protein synthesis, is to decode RNA into
a chain of amino acids which forms a protein. Called
Central Dogma
DNA (transcription) RNA  (translation) Proteins
• Proteins are made by joining amino acids into long chains
Functions of a Protein
• Structural
– muscle, hair
• Chemical / Functional
– antibodies, hormones, enzymes
• Involved in protein synthesis
• Made up of nucleotides:
• A phosphate group
• A sugar (ribose)
• Nitrogenous bases
• (RNA only has A, U, C, G there is no T!)
• There are three types of RNA
• mRNA – (Messenger RNA) copy of DNA containing
instructions for assembling proteins. Created in the nucleus.
• Ribosomes are made of
rRNA. Attaches individual
amino acids together.
• tRNA - brings amino acids to
the ribosome.
• Flow of info: DNA  mRNA
• Location: Nucleus
• mRNA is produced by copying a section/gene of
the DNA (RNA Polymerase)
• Where does the mRNA go?
– Cytoplasm/Ribosomes
Transcription Animation
End of Transcription
• Flow of info: mRNA  Proteins
• Location: Cytoplasm/Ribosomes
• Decoding mRNA into a chain of amino acids (protein)
• A ribosome (rRNA) attaches to the mRNA
• The mRNA code is read 3 letters/bases at a time (codon)
• The start codon (AUG) tells the rRNA to begin adding amino acids.
•The tRNA (with amino acid) that pairs with the codon will come
to the ribosome and bind to the mRNA.
•The ribosome adds new tRNA molecules and amino acids as it
moves along the mRNA.
As each new tRNA enters the
ribosome, one leaves.
Before tRNA can leave the
ribosome, the amino acids will
bond together to make a
polypeptide (protein) chain
• The process
continues until the
ribosome reaches a
stop codon.
Translation Animation
Full Process Animation
(Transcription & Translation)
Amoeba Sisters - Protein Synthesis
Gene Expression / Protein Synthesis